In recent years, fiber laser devices have been used in processing machines for performing processing with laser light, medical devices such as surgical knives using laser light, and the like. In a fiber laser device, laser light generated from a laser oscillator and pumping light are incident on an amplification optical fiber, and the amplified laser light is emitted from an output unit.
In such a fiber laser device, a certain period of time is required for the intensity of laser light to be stabilized from when the laser light is started to be emitted from the fiber laser device. That is, a certain period of time is required for laser light to rise.
As the rise time of laser light becomes shorter, the work efficiency becomes higher. Patent Document 1 listed below discloses a fiber laser device that requires a short period of time to stabilize the intensity of laser light.
In the fiber laser device disclosed in Patent Document 1 listed below, pumping light with a low and constant intensity is incident on an amplification optical fiber during the periods other than the periods during which laser light is emitted from the fiber laser device, and a rare-earth element doped in the amplification optical fiber is pumped. That is, pre-pumping is performed during the periods other than the periods during which laser light is emitted from the fiber laser device. When laser light is emitted from the fiber laser device, seed laser light and pumping light with a high intensity are incident on the amplification optical fiber, and amplified laser light is emitted. In this manner, when laser light is emitted from the fiber laser device, the rare-earth element in the amplification optical fiber is pumped by pre-pumping. Accordingly, the rise time of the laser light emitted from the fiber laser device is short (Patent Document 1).